1. Field of the Invention
The present invention relates to apparatus and methods for managing the exploitation of a subterranean reservoir. In another aspect, the present invention relates to apparatus and methods for producing hydrocarbons from a subterranean hydrocarbon reservoir. In even another aspect, the present invention relates to apparatus and methods for producing hydrocarbons utilizing modeling and monitoring of the subterrane hydrocarbon reservoir. In still another aspect, the present invention relates to the use of seismic data. In yet another aspect, the present invention relates to the use of time lapse vertical seismic profile data to monitor and model the subterranean hydrocarbon reservoir. In even still another aspect, the present invention relates to a method and apparatus for producing hydrocarbons from a subterranean reservoir utilizing seismic sensors, computer modeling of the reservoir from gathered seismic data, and iterative modeling with respect to time as more seismic, reservoir and production data are gathered. In even yet another aspect, the present invention relates to computer implemented methods and apparatus for monitoring and modeling a subterranean reservoir, computer readable media having stored thereon instructions for carrying out and forming such computer implemented methods and apparatus, and a propagated data signal or computer data signal having such instructions.
2. Description of the Related Art
Historically, most oil and gas reservoirs have been developed and managed by first conducting a preliminary investigation of an area using broad geological methods for collection and analysis of data such as seismic, gravimetric, and magnetic data, to determine regional geology and subsurface reservoir structure. In some instances, more detailed seismic mapping of a specific structure was conducted in an effort to reduce the high cost, and the high risk, of an exploration well.
A test well was then drilled to penetrate the identified structure to confirm the presence of hydrocarbons, and to test productivity. In lower-cost onshore areas, development of a field would commence immediately by completing the test well as a production well. In higher cost or more hostile environments such as the North Sea, a period of appraisal would follow, leading to a decision as to whether or not to develop the project. In either case, based on inevitably sparse data, further development wells, both producers and injectors would be planned in accordance with a reservoir development plan.
Once production and/or injection began, more dynamic data would become available, thus, allowing the engineers and geoscientists to better understand how the reservoir rock were distributed and how the fluids were flowing. As more data became available, an improved understanding of the reservoir was used to adjust the reservoir development plan resulting in the familiar pattern of development drilling, infill drilling, recompletions, sidetracks, well abandonment, etc.
Unfortunately, reservoir engineers typically gain knowledge in a fashion similar to pathologists who learn everything upon a patient""s demise, because it is not until the time at which the field is abandoned, and when the information is the least useful, that reservoir understanding reaches its maximum.
Limited and relatively poor quality of reservoir data throughout the life of the reservoir, coupled with the relatively high cost of most types of well intervention, implies that reservoir management is as much an art as a science. Engineers and geoscientists responsible for reservoir management discussed injection, fingering, fluid movement, gas oil ratio changes, and pressure front movement as if these were precise defined processes. The reality, however, is that water predicted to take three years to break through to a producing well might arrive in six months in one reservoir but might never appear in another. Text book like xe2x80x9cpiston likexe2x80x9d displacement rarely happens, and one could only guess at actual fluid movement.
For some time, reservoir engineers and geoscientists have made assessments of reservoir characteristics and optimized production using down hole test data taken at selected intervals. Such data usually includes pressure, composition, temperature and flow data as well known in the art. Reservoir engineers have also had access to production data for the individual wells in a reservoir. Such data as oil, water and gas flow rates are generally obtained by selectively testing production from the selected well at selected intervals.
Recent improvements in the state of the art regarding data gathering, both down hole and at the surface, have dramatically increased the quantity and quality of data gathered. Examples of such state of the art improvements in data acquisition technology include assemblies run in the casing string comprising a sensor probe with optional flow ports that allow fluid inflow from the formation into the casing while sensing wellbore and/or reservoir characteristics. The casing assembly may further include a microprocessor, a transmitting device, and a controlling device located in the casing string for processing and transmitting real time data. A memory device may also be provided for recording data relating to the monitored wellbore or reservoir characteristics. Examples of reservoir characteristics which may be monitored with such equipment include: temperature, pressure, fluid flow rate and type, formation resistivity, cross-well seismology and acoustic seismometry, perforation depth, fluid characteristics and logging data. Using a microprocessor, hydrocarbon production performance may be enhanced by activating local operations in additional downhole equipment.
Recent technology improvements include downhole flow control devices which may be used to shut off particular zones by using downhole electronics and programing with decision making capacity, the disclosure of which is incorporated by reference.
Another important emerging technology that may have a substantial impact on managing reservoirs is time lapse seismic, often referred to as 4-D seismic. In the past, seismic surveys were conducted primarily for exploration purposes. However, incremental differences in seismic data gathered over time are becoming useful as a reservoir management tool to potentially detect dynamic reservoir fluid movement. This is accomplished by removing the non-time varying seismic elements to produce a direct image of the time-varying changes caused by, for example, fluid saturation, pressure, temperature, and other physical changes which may occur in the reservoir over time. By using 4-D seismic data, reservoir engineers and geoscientists can locate bypassed oil to optimize reservoir management. Additionally, 4-D seismic processing can be used to enhance the reservoir model and history match flow simulations.
International PCT application WO 98/07049, the disclosure of which is incorporated herein by reference, describes and discloses state of the art seismic technology applicable for gathering data relevant to a producing reservoir. The publication discloses a reservoir monitoring system comprising: a plurality of permanently coupled remote sensor nodes, wherein each node comprises a plurality of seismic sensors and a digitizer for analog signals; a concentrator of signals received from the plurality of permanently coupled remote sensor nodes; a plurality of remote transmission lines which independently connect each of the plurality of remote sensor nodes to the concentrator; a recorder of the concentrated signals from the concentrator; and a transmission line which connects the concentrator to the recorder. The system is used to transmit remote data signals independently from each node of the plurality of permanently coupled remote sensor nodes to a concentrator and then transmit the concentrated data signals to a recorder. Such advanced systems of gathering seismic data may be used in the reservoir management system of the present invention as disclosed hereinafter in the Detailed Description section of the application.
Historically, down hole data and surface production data have been analyzed by pressure tests and production analysis. Presently, a number of commercially available computer programs such as Saphir and PTA are available to do such an analysis. The pressure transient analysis generates output data well known in the art, such as permeability-feet, skin, average reservoir pressure and the estimated reservoir boundaries. Such reservoir parameters may be used in the reservoir management system of the present invention.
In the past and present, geoscientists (sometimes in conjunction with reservoir engineers) analyzed well log data and core data. The data was and may currently be processed in log processing/interpretation programs that are commercially available, such as the commercially available Petroworks and DPP programs available from Halliburton. Seismic data may be processed in programs such as the commercially available Seisworks programs available from Hallibruton and then the log data and seismic data are processed together and often geostatistics applied to create a geocellular model.
Presently, reservoir engineers may use reservoir simulators such as Halliburton""s VIP tools in the analysis of the reservoir. Nodal analysis programs such as WEM, Prosper and Openflow have been used in conjunction with material balance programs and economic analysis programs such as Halliburton""s ResEV and Aries programs to generate a desired field wide production forecast. Once the field wide production has been forecasted, selected wells may be produced at the computed rates to obtain the projected forecast rate. Likewise, such analysis is used to determine field wide injection rates for maintenance of reservoir pressure and for water flood pattern development. In a similar manner, target injection rates and zonal profiles are determined to obtain the field wide injection rates.
It is estimated that between fifty and seventy percent of a reservoir engineer""s time is spent manipulating data for use by each of the computer programs in order for the data gathered and processed by the disparate programs (developed by different companies) to obtain a resultant output desired field wide production forecast. Due to the complexity and time required to perform these functions, frequently an abbreviated incomplete analysis is performed with the output used to adjust production parameters for better reservoir performance never knowing how such adjustment will affect reservoir management as a whole.
A number of patents have been directed to management of production from a hydrocarbon reservoir. U.S. Pat. No. 4,676,313, issued Jun. 30, 1987, to Rinaldi discloses a method of enhancing oil and/or gas recovery by properly drilling injection and production wells into a reservoir, incorporating flow control valves and sensors in both sets of wells, and connecting these valves and sensors to a surface computer. The computer compares the fluid flow data from the valves and sensors to a theoretical flow model of the reservoir to determine actual fluid flow paths in the reservoir, and then determines the optimum fluid flow rates and paths and adjusts the valve open-close patterns and settings accordingly, to force the reservoir fluid flows into those paths. The computer continually performs these operations so as to constantly provide maximum sweep efficiency and therefore optimum reservoir productivity. In conjunction with the above methodology, the densities and viscosities of the injected fluids can be varied so that they can assist with the movement of fluids within the reservoir.
U.S. Pat. No. 5,662,165, issued Sep. 2, 1997, and U.S. Pat. No. 6,006,832, issued Dec. 28, 1999, both related and issued to Tubel, et al., disclose a method and system for monitoring and controlling production and injection wells having permanent downhole formation evaluation sensors. These formation evaluation sensors may include, for example, neutron generator, gamma ray detector and resistivity sensors which can, in real time, sense and evaluate formation parameters including important information regarding formation invading water entering the producing zone. Significantly, this information can be obtained prior to the water actually entering the producing geological formation and therefore corrective action (i.e., closing of a valve or sliding sleeve) can be taken prior to water being produced. This real time acquisition of formation data in the production well constitutes an important advance over current wireline techniques in that the present invention is far less costly and can anticipate and react to potential problems before they occur. In addition, the formation evaluation sensors themselves can be placed much closer to the actual formation (i.e., adjacent the casing or downhole completion tool) than wireline devices which are restricted to the interior of the production tubing.
U.S. Pat. No. 5,597,042, issued Jan. 28, 1997, to Tubel et al., and also related to ""165 and ""832 above, discloses a method and system for monitoring a formation surrounding a borehole in a production well. The method encompasses the use of a downhole sensor permanently mounted in the well to sense at least one downhole formation parameter which is not normally present within the wellbore. The system includes a formation evaluation sensor permanently located downhole in a production well having at least two boreholes, wherein at least one of the boreholes is a branch borehole, the sensor sensing a formation parameter which is not normally present within the borehole.
U.S. Pat. No. 5,992,519, issued Nov. 30, 1999, to Ramakrishnan, et al., discloses real time monitoring and control of downhole reservoirs. The method for the active or automated control of the reservoir uses a reservoir model with available data such as seismic, log, and core data as inputs, and uses the reservoir model in conjunction with a reservoir simulation tool in order to determine a production strategy which will maximize certain criteria, e.g., profits. The production strategy may include fixed elements which are not easily altered once the wells go into production, and variable elements which can be adjusted without serious effort during production. The production strategy is implemented by drilling wells, etc., and fluids are then controllably produced from the reservoir according to the variable production strategy; i.e., fluid flow rates are monitored by sensors, and, by adjusting control valves, are kept to desired values (which may change over time) set according to the variable production strategy. According to another aspect of the invention, information gleaned as a result of the adjustments to the control means is used to update the reservoir model. As a result, the variable and fixed production strategies can be updated and implemented.
However, in spite of the above advancements, there still exists a need in the art for apparatus and methods for producing hydrocarbons from a subterranean reservoir.
There is also the need in the art for apparatus and methods for producing hydrocarbons from a subterranean reservoir which do not suffer from the disadvantages of the prior art.
These and other needs in the art will become apparent to those of skill in the art upon review of this specification, including its drawings and claims.
It is an object of the present invention to provide for apparatus and methods for producing hydrocarbons from a subterranean reservoir.
It is another object of the present invention to provide for apparatus and methods for producing hydrocarbons from a subterranean reservoir which do not suffer from the disadvantages of the prior art.
These and other objects of the present invention will become apparent to those of skill in the art upon review of this specification, including its drawings and claims.
According to one embodiment of the present invention there is provided a method for monitoring a reservoir in the subterrane. The method includes any combination in any order of one or more of the following steps: (a) screening the reservoir to determine if the reservoir comprises at least one suitable property selected from the group consisting of geologic properties, fluid properties, dry rock properties and saturated rock properties; (b) modeling the reservoir to determine if vertical seismic profiling of the reservoir over time will provide a suitable time variant response; (c) generating model seismic data from a model of the subterrane; (d) modifying the model of the subterrane based on a comparison to current vertical seismic profile data, to create a modified model of the subterrane which now becomes the model of the subterrane; (e) carrying out steps (c) and (d) until the differences between the model seismic data and the vertical seismic profile data are as desired; (f) obtaining model production data from a reservoir model derived from the model of the subterrane, and if the differences between the reservoir model data and actual production data are not as desired, modifying the model of the subterrane to create an updated model of the subterrane which now becomes the model of the subterrane, and returning to step (c); (g) generating seismic model data for a certain time t from the reservoir model; and (h) comparing the seismic model data with actual seismic data for the certain time t, and if the differences are not as desired either modify the reservoir model and return to step (f) or modify the model of the subterrane and return to step (c).
According to another embodiment of the present invention, there is provided an apparatus for monitoring a reservoir in the subterrane, the apparatus comprising a computer and comprising programming code which when executed causes the computer to carry out any combination in any order of one or more of the following: (a) model the reservoir to determine if vertical seismic profiling of the reservoir over time will provide a suitable time variant response; (b) generate model seismic data from a model of the subterrane; (c) modify the model of the subterrane based on a comparison to current vertical seismic profile data, to create a modified model of the subterrane which now becomes the model of the subterrane; (d) carry out steps (c) and (d) until the differences between the model seismic data and the vertical seismic profile data are as desired; (e) obtain model production data from a reservoir model derived from the model of the subterrane, and if the differences between the reservoir model data and actual production data are not as desired, modifying the model of the subterrane to create an updated model of the subterrane which now becomes the model of the subterrane, and returning to step (c); (f) generate seismic model data for a certain time t from the reservoir model; and (g) compare the seismic model data with actual seismic data for the certain time t, and if the differences are not as desired either modify the reservoir model and return to step (f) or modify the model of the subterrane and return to step (c).
According to even another embodiment of the present invention, there is provided computer readable media embodying programming code for monitoring a reservoir in the subterrane, the programming code which when executed causes the computer to carry out any combination in any order of one or more of the following: (a) model the reservoir to determine if vertical seismic profiling of the reservoir over time will provide a suitable time variant response; (b) generate model seismic data from a model of the subterrane; (c) modify the model of the subterrane based on a comparison to current vertical seismic profile data, to create a modified model of the subterrane which now becomes the model of the subterrane; (d) carry out steps (c) and (d) until the differences between the model seismic data and the vertical seismic profile data are as desired; (e) obtain model production data from a reservoir model derived from the model of the subterrane, and if the differences between the reservoir model data and actual production data are not as desired, modifying the model of the subterrane to create an updated model of the subterrane which now becomes the model of the subterrane, and returning to step (c); (f) generate seismic model data for a certain time t from the reservoir model; and (g) compare the seismic model data with actual seismic data for the certain time t, and if the differences are not as desired either modify the reservoir model and return to step (f) or modify the model of the subterrane and return to step (c).
According to even another embodiment of the present invention, the is provided a data signal embodying programming code for monitoring a reservoir in the subterrane, the programming code which when executed causes the computer to carry out any combination in any order of one or more of the following: (a) model the reservoir to determine if vertical seismic profiling of the reservoir over time, will provide a suitable time variant response; (b) generate model seismic data from a model of the subterrane; (c) modify the model of the subterrane based on a comparison to current vertical seismic profile data, to create a modified model of the subterrane which now becomes the model of the subterrane; (d) carry out steps (c) and (d) until the differences between the model seismic data and the vertical seismic profile data are as desired; (e) obtain model production data from a reservoir model derived from the model of the subterrane, and if the differences between the reservoir model data and actual production data are not as desired, modifying the model of the subterrane to create an updated model of the subterrane which now becomes the model of the subterrane, and returning to step (c); (f) generate seismic model data for a certain time t from the reservoir model; and (g) compare the seismic model data with actual seismic data for the certain time t, and if the differences are not as desired either modify the reservoir model and return to step (f) or modify the model of the subterrane and return to step (c).
These and other embodiments of the present invention will become apparent to those of skill in the art upon review of this specification, including its drawings and claims.